Use umtx to implement process sharable semaphore, to make this work,

now type sema_t is a structure which can be put in a shared memory area,
and multiple processes can operate it concurrently.
User can either use mmap(MAP_SHARED) + sem_init(pshared=1) or use sem_open()
to initialize a shared semaphore.
Named semaphore uses file system and is located in /tmp directory, and its
file name is prefixed with 'SEMD', so now it is chroot or jail friendly.
In simplist cases, both for named and un-named semaphore, userland code
does not have to enter kernel to reduce/increase semaphore's count.
The semaphore is designed to be crash-safe, it means even if an application
is crashed in the middle of operating semaphore, the semaphore state is
still safely recovered by later use, there is no waiter counter maintained
by userland code.
The main semaphore code is in libc and libthr only has some necessary stubs,
this makes it possible that a non-threaded application can use semaphore
without linking to thread library.
Old semaphore implementation is kept libc to maintain binary compatibility.
The kernel ksem API is no longer used in the new implemenation.

Discussed on: threads@

18 files changed, 924 insertions, 402 deletions

diff --git a/ObsoleteFiles.inc b/ObsoleteFiles.inc
index 52ca682..784c8de 100644
--- a/ObsoleteFiles.inc
+++ b/ObsoleteFiles.inc
@@ -14,6 +14,8 @@
 # The file is partitioned: OLD_FILES first, then OLD_LIBS and OLD_DIRS last.
 #
 
+# 20100105: new userland semaphore implementation
+OLD_FILES+=usr/include/sys/semaphore.h
 # 20100103: ntptrace(8) removed
 OLD_FILES+=usr/sbin/ntptrace
 OLD_FILES+=usr/share/man/man8/ntptrace.8.gz
diff --git a/include/Makefile b/include/Makefile
index 2b0ea22..68a7e8d 100644
--- a/include/Makefile
+++ b/include/Makefile
@@ -18,7 +18,7 @@ INCS=	a.out.h ar.h assert.h bitstring.h complex.h cpio.h _ctype.h ctype.h \
 	netdb.h nl_types.h nlist.h nss.h nsswitch.h paths.h \
 	printf.h proc_service.h pthread.h \
 	pthread_np.h pwd.h ranlib.h readpassphrase.h regex.h regexp.h \
-	res_update.h resolv.h runetype.h search.h setjmp.h \
+	res_update.h resolv.h runetype.h search.h semaphore.h setjmp.h \
 	signal.h spawn.h stab.h \
 	stdbool.h stddef.h stdio.h stdlib.h string.h stringlist.h \
 	strings.h sysexits.h tar.h termios.h tgmath.h \
@@ -28,7 +28,7 @@ INCS=	a.out.h ar.h assert.h bitstring.h complex.h cpio.h _ctype.h ctype.h \
 
 MHDRS=	float.h floatingpoint.h stdarg.h
 
-PHDRS=	sched.h semaphore.h _semaphore.h
+PHDRS=	sched.h _semaphore.h
 
 LHDRS=	aio.h errno.h fcntl.h linker_set.h poll.h stdint.h syslog.h \
 	ucontext.h
diff --git a/include/semaphore.h b/include/semaphore.h
new file mode 100644
index 0000000..3531353
--- /dev/null
+++ b/include/semaphore.h
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2010 David Xu <davidxu@freebsd.org>
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice unmodified, this list of conditions, and the following
+ *    disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+/* semaphore.h: POSIX 1003.1b semaphores */
+
+#ifndef _SEMAPHORE_H_
+#define _SEMAPHORE_H_
+
+#include <sys/cdefs.h>
+#include <sys/_types.h>
+#include <sys/_umtx.h>
+
+struct _sem {
+	__uint32_t	_magic;
+	struct _usem	_kern;
+};
+
+typedef	struct _sem	sem_t;
+
+#define	SEM_FAILED	((sem_t *)0)
+#define	SEM_VALUE_MAX	__INT_MAX
+
+struct timespec;
+
+__BEGIN_DECLS
+int	 sem_close(sem_t *);
+int	 sem_destroy(sem_t *);
+int	 sem_getvalue(sem_t * __restrict, int * __restrict);
+int	 sem_init(sem_t *, int, unsigned int);
+sem_t	*sem_open(const char *, int, ...);
+int	 sem_post(sem_t *);
+int	 sem_timedwait(sem_t * __restrict, const struct timespec * __restrict);
+int	 sem_trywait(sem_t *);
+int	 sem_unlink(const char *);
+int	 sem_wait(sem_t *);
+__END_DECLS
+
+#endif /* !_SEMAPHORE_H_ */
diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
index d6b403e..2abfe57 100644
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -25,7 +25,7 @@ SRCS+=  __getosreldate.c __xuname.c \
 	pause.c pmadvise.c popen.c posix_spawn.c \
 	psignal.c pw_scan.c pwcache.c \
 	raise.c readdir.c readpassphrase.c rewinddir.c \
-	scandir.c seed48.c seekdir.c sem.c semctl.c \
+	scandir.c seed48.c seekdir.c sem.c sem_new.c semctl.c \
 	setdomainname.c sethostname.c setjmperr.c setmode.c \
 	setproctitle.c setprogname.c siginterrupt.c siglist.c signal.c \
 	sigsetops.c sleep.c srand48.c statvfs.c stringlist.c strtofflags.c \
diff --git a/lib/libc/gen/Symbol.map b/lib/libc/gen/Symbol.map
index a3ea75b..4f75b73 100644
--- a/lib/libc/gen/Symbol.map
+++ b/lib/libc/gen/Symbol.map
@@ -236,16 +236,6 @@ FBSD_1.0 {
 	seekdir;
 	user_from_uid;
 	group_from_gid;
-	sem_init;
-	sem_destroy;
-	sem_open;
-	sem_close;
-	sem_unlink;
-	sem_wait;
-	sem_trywait;
-	sem_timedwait;
-	sem_post;
-	sem_getvalue;
 	setdomainname;
 	sethostname;
 	longjmperror;
@@ -363,11 +353,23 @@ FBSD_1.1 {
 	semctl;
 	tcgetsid;
 	tcsetsid;
+	__pthread_cleanup_pop_imp;
+	__pthread_cleanup_push_imp;
 };
 
 FBSD_1.2 {
 	basename_r;
 	getpagesizes;
+	sem_close;
+	sem_destroy;
+	sem_getvalue;
+	sem_init;
+	sem_open;
+	sem_timedwait;
+	sem_trywait;
+	sem_post;
+	sem_wait;
+	sem_unlink;
 };
 
 FBSDprivate_1.0 {
@@ -456,16 +458,6 @@ FBSDprivate_1.0 {
 	__pw_scan;	/* Used by (at least) libutil */
 	__raise;
 	_raise;
-	__sem_init;
-	__sem_destroy;
-	__sem_open;
-	__sem_close;
-	__sem_unlink;
-	__sem_wait;
-	__sem_trywait;
-	__sem_timedwait;
-	__sem_post;
-	__sem_getvalue;
 	__sleep;
 	_sleep;
 	_rtld_allocate_tls;
@@ -482,4 +474,23 @@ FBSDprivate_1.0 {
 	_wait;
 	__waitpid;
 	_waitpid;
+
+	_libc_sem_destroy;
+	_libc_sem_init;
+	_libc_sem_getvalue;
+	_libc_sem_trywait;
+	_libc_sem_wait;
+	_libc_sem_timedwait;
+	_libc_sem_post;
+
+	_libc_sem_init_compat;
+	_libc_sem_destroy_compat;
+	_libc_sem_open_compat;
+	_libc_sem_close_compat;
+	_libc_sem_unlink_compat;
+	_libc_sem_wait_compat;
+	_libc_sem_trywait_compat;
+	_libc_sem_timedwait_compat;
+	_libc_sem_post_compat;
+	_libc_sem_getvalue_compat;
 };
diff --git a/lib/libc/gen/_pthread_stubs.c b/lib/libc/gen/_pthread_stubs.c
index 147235e..044e299e 100644
--- a/lib/libc/gen/_pthread_stubs.c
+++ b/lib/libc/gen/_pthread_stubs.c
@@ -119,6 +119,8 @@ pthread_func_entry_t __thr_jtable[PJT_MAX] = {
 	{PJT_DUAL_ENTRY(stub_zero)},    /* PJT_SETSPECIFIC */
 	{PJT_DUAL_ENTRY(stub_zero)},    /* PJT_SIGMASK */
 	{PJT_DUAL_ENTRY(stub_zero)},    /* PJT_TESTCANCEL */
+	{PJT_DUAL_ENTRY(stub_zero)},    /* PJT_CLEANUP_POP_IMP */
+	{PJT_DUAL_ENTRY(stub_zero)},    /* PJT_CLEANUP_PUSH_IMP */
 };
 
 /*
@@ -265,6 +267,8 @@ STUB_FUNC2(pthread_kill, PJT_KILL, int, void *, int)
 STUB_FUNC2(pthread_setcancelstate, PJT_SETCANCELSTATE, int, int, void *)
 STUB_FUNC2(pthread_setcanceltype, PJT_SETCANCELTYPE, int, int, void *)
 STUB_FUNC(pthread_testcancel, PJT_TESTCANCEL, void)
+STUB_FUNC1(__pthread_cleanup_pop_imp, PJT_CLEANUP_POP_IMP, int, int)
+STUB_FUNC2(__pthread_cleanup_push_imp, PJT_CLEANUP_PUSH_IMP, void, void*, void *);
 
 static int
 stub_zero(void)
diff --git a/lib/libc/gen/sem.c b/lib/libc/gen/sem.c
index cd31d31..4ec7890 100644
--- a/lib/libc/gen/sem.c
+++ b/lib/libc/gen/sem.c
@@ -1,4 +1,5 @@
 /*
+ * Copyright (C) 2010 David Xu <davidxu@freebsd.org>.
  * Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
  * All rights reserved.
  * 
@@ -59,34 +60,71 @@
 #include "namespace.h"
 #include <sys/types.h>
 #include <sys/queue.h>
+#include <machine/atomic.h>
 #include <errno.h>
+#include <sys/umtx.h>
+#include <sys/_semaphore.h>
+#include <limits.h>
 #include <fcntl.h>
 #include <pthread.h>
-#include <semaphore.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <time.h>
-#include <_semaphore.h>
 #include "un-namespace.h"
 #include "libc_private.h"
 
+/*
+ * Old semaphore definitions.
+ */
+struct sem {
+#define SEM_MAGIC       ((u_int32_t) 0x09fa4012)
+        u_int32_t       magic;
+        pthread_mutex_t lock;
+        pthread_cond_t  gtzero;
+        u_int32_t       count;
+        u_int32_t       nwaiters;
+#define SEM_USER        (NULL)
+        semid_t         semid;  /* semaphore id if kernel (shared) semaphore */
+        int             syssem; /* 1 if kernel (shared) semaphore */
+        LIST_ENTRY(sem) entry;
+        struct sem      **backpointer;
+};
+
+typedef struct sem* sem_t;
+
+#define SEM_FAILED     ((sem_t *)0)
+#define SEM_VALUE_MAX  __INT_MAX
+
+#define SYM_FB10(sym)                   __CONCAT(sym, _fb10)
+#define SYM_FBP10(sym)                  __CONCAT(sym, _fbp10)
+#define WEAK_REF(sym, alias)            __weak_reference(sym, alias)
+#define SYM_COMPAT(sym, impl, ver)      __sym_compat(sym, impl, ver)
+#define SYM_DEFAULT(sym, impl, ver)     __sym_default(sym, impl, ver)
+ 
+#define FB10_COMPAT(func, sym)                          \
+        WEAK_REF(func, SYM_FB10(sym));                  \
+        SYM_COMPAT(sym, SYM_FB10(sym), FBSD_1.0)
+
+#define FB10_COMPAT_PRIVATE(func, sym)                  \
+        WEAK_REF(func, SYM_FBP10(sym));                 \
+        SYM_DEFAULT(sym, SYM_FBP10(sym), FBSDprivate_1.0)
+
 static sem_t sem_alloc(unsigned int value, semid_t semid, int system_sem);
 static void  sem_free(sem_t sem);
 
-static LIST_HEAD(, sem) named_sems = LIST_HEAD_INITIALIZER(named_sems);
+static LIST_HEAD(, sem) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
 static pthread_mutex_t named_sems_mtx = PTHREAD_MUTEX_INITIALIZER;
 
-__weak_reference(__sem_init, sem_init);
-__weak_reference(__sem_destroy, sem_destroy);
-__weak_reference(__sem_open, sem_open);
-__weak_reference(__sem_close, sem_close);
-__weak_reference(__sem_unlink, sem_unlink);
-__weak_reference(__sem_wait, sem_wait);
-__weak_reference(__sem_trywait, sem_trywait);
-__weak_reference(__sem_timedwait, sem_timedwait);
-__weak_reference(__sem_post, sem_post);
-__weak_reference(__sem_getvalue, sem_getvalue);
-
+FB10_COMPAT(_libc_sem_init_compat, sem_init);
+FB10_COMPAT(_libc_sem_destroy_compat, sem_destroy);
+FB10_COMPAT(_libc_sem_open_compat, sem_open);
+FB10_COMPAT(_libc_sem_close_compat, sem_close);
+FB10_COMPAT(_libc_sem_unlink_compat, sem_unlink);
+FB10_COMPAT(_libc_sem_wait_compat, sem_wait);
+FB10_COMPAT(_libc_sem_trywait_compat, sem_trywait);
+FB10_COMPAT(_libc_sem_timedwait_compat, sem_timedwait);
+FB10_COMPAT(_libc_sem_post_compat, sem_post);
+FB10_COMPAT(_libc_sem_getvalue_compat, sem_getvalue);
 
 static inline int
 sem_check_validity(sem_t *sem)
@@ -104,8 +142,6 @@ static void
 sem_free(sem_t sem)
 {
 
-	_pthread_mutex_destroy(&sem->lock);
-	_pthread_cond_destroy(&sem->gtzero);
 	sem->magic = 0;
 	free(sem);
 }
@@ -131,13 +167,11 @@ sem_alloc(unsigned int value, semid_t semid, int system_sem)
 	sem->magic = SEM_MAGIC;
 	sem->semid = semid;
 	sem->syssem = system_sem;
-	sem->lock = PTHREAD_MUTEX_INITIALIZER;
-	sem->gtzero = PTHREAD_COND_INITIALIZER;
 	return (sem);
 }
 
 int
-__sem_init(sem_t *sem, int pshared, unsigned int value)
+_libc_sem_init_compat(sem_t *sem, int pshared, unsigned int value)
 {
 	semid_t semid;
 
@@ -147,26 +181,27 @@ __sem_init(sem_t *sem, int pshared, unsigned int value)
 	 * pthread_cond_wait() is just a stub that doesn't really
 	 * wait.
 	 */
-	if (ksem_init(&semid, value) != 0)
+	semid = (semid_t)SEM_USER;
+	if ((pshared != 0) && ksem_init(&semid, value) != 0)
 		return (-1);
 
-	(*sem) = sem_alloc(value, semid, 1);
+	*sem = sem_alloc(value, semid, pshared);
 	if ((*sem) == NULL) {
-		ksem_destroy(semid);
+		if (pshared != 0)
+			ksem_destroy(semid);
 		return (-1);
 	}
 	return (0);
 }
 
 int
-__sem_destroy(sem_t *sem)
+_libc_sem_destroy_compat(sem_t *sem)
 {
 	int retval;
 
 	if (sem_check_validity(sem) != 0)
 		return (-1);
 
-	_pthread_mutex_lock(&(*sem)->lock);
 	/*
 	 * If this is a system semaphore let the kernel track it otherwise
 	 * make sure there are no waiters.
@@ -181,18 +216,14 @@ __sem_destroy(sem_t *sem)
 		retval = 0;
 		(*sem)->magic = 0;
 	}
-	_pthread_mutex_unlock(&(*sem)->lock);
 
-	if (retval == 0) {
-		_pthread_mutex_destroy(&(*sem)->lock);
-		_pthread_cond_destroy(&(*sem)->gtzero);
+	if (retval == 0)
 		sem_free(*sem);
-	}
 	return (retval);
 }
 
 sem_t *
-__sem_open(const char *name, int oflag, ...)
+_libc_sem_open_compat(const char *name, int oflag, ...)
 {
 	sem_t *sem;
 	sem_t s;
@@ -255,7 +286,7 @@ err:
 }
 
 int
-__sem_close(sem_t *sem)
+_libc_sem_close_compat(sem_t *sem)
 {
 
 	if (sem_check_validity(sem) != 0)
@@ -280,68 +311,156 @@ __sem_close(sem_t *sem)
 }
 
 int
-__sem_unlink(const char *name)
+_libc_sem_unlink_compat(const char *name)
 {
 
 	return (ksem_unlink(name));
 }
 
-int
-__sem_wait(sem_t *sem)
+static int
+enable_async_cancel(void)
 {
+	int old;
 
-	if (sem_check_validity(sem) != 0)
+	_pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &old);
+	return (old);
+}
+
+static void
+restore_async_cancel(int val)
+{
+	_pthread_setcanceltype(val, NULL);
+}
+
+static int
+_umtx_wait_uint(volatile unsigned *mtx, unsigned id, const struct timespec *timeout)
+{
+	if (timeout && (timeout->tv_sec < 0 || (timeout->tv_sec == 0 &&
+	    timeout->tv_nsec <= 0))) {
+		errno = ETIMEDOUT;
 		return (-1);
+	}
+	return _umtx_op(__DEVOLATILE(void *, mtx),
+		UMTX_OP_WAIT_UINT_PRIVATE, id, NULL, __DECONST(void*, timeout));
+}
 
-	return (ksem_wait((*sem)->semid));
+static int
+_umtx_wake(volatile void *mtx)
+{
+	return _umtx_op(__DEVOLATILE(void *, mtx), UMTX_OP_WAKE_PRIVATE,
+			1, NULL, NULL);
+}
+
+#define TIMESPEC_SUB(dst, src, val)                             \
+        do {                                                    \
+                (dst)->tv_sec = (src)->tv_sec - (val)->tv_sec;  \
+                (dst)->tv_nsec = (src)->tv_nsec - (val)->tv_nsec; \
+                if ((dst)->tv_nsec < 0) {                       \
+                        (dst)->tv_sec--;                        \
+                        (dst)->tv_nsec += 1000000000;           \
+                }                                               \
+        } while (0)
+
+
+static void
+sem_cancel_handler(void *arg)
+{
+	sem_t *sem = arg;
+
+	atomic_add_int(&(*sem)->nwaiters, -1);
+	if ((*sem)->nwaiters && (*sem)->count)
+		_umtx_wake(&(*sem)->count);
 }
 
 int
-__sem_trywait(sem_t *sem)
+_libc_sem_timedwait_compat(sem_t * __restrict sem,
+	const struct timespec * __restrict abstime)
 {
-	int retval;
+	struct timespec ts, ts2;
+	int val, retval, saved_cancel;
 
 	if (sem_check_validity(sem) != 0)
 		return (-1);
 
-	if ((*sem)->syssem != 0)
- 		retval = ksem_trywait((*sem)->semid);
-	else {
-		_pthread_mutex_lock(&(*sem)->lock);
-		if ((*sem)->count > 0) {
-			(*sem)->count--;
-			retval = 0;
-		} else {
-			errno = EAGAIN;
-			retval = -1;
+	if ((*sem)->syssem != 0) {
+		saved_cancel = enable_async_cancel();
+		retval = ksem_wait((*sem)->semid);
+		restore_async_cancel(saved_cancel);
+		return (retval);
+	}
+
+	retval = 0;
+	_pthread_testcancel();
+	for (;;) {
+		while ((val = (*sem)->count) > 0) {
+			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
+				return (0);
+		}
+		if (retval)
+			break;
+		if (abstime) {
+			if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
+				errno = EINVAL;
+				return (-1);
+			}
+			clock_gettime(CLOCK_REALTIME, &ts);
+	                TIMESPEC_SUB(&ts2, abstime, &ts);
 		}
-		_pthread_mutex_unlock(&(*sem)->lock);
+		atomic_add_int(&(*sem)->nwaiters, 1);
+		pthread_cleanup_push(sem_cancel_handler, sem);
+		saved_cancel = enable_async_cancel();
+		retval = _umtx_wait_uint(&(*sem)->count, 0, abstime ? &ts2 : NULL);
+		restore_async_cancel(saved_cancel);
+		pthread_cleanup_pop(0);
+		atomic_add_int(&(*sem)->nwaiters, -1);
 	}
 	return (retval);
 }
 
 int
-__sem_timedwait(sem_t * __restrict sem,
-    const struct timespec * __restrict abs_timeout)
+_libc_sem_wait_compat(sem_t *sem)
 {
+	return _libc_sem_timedwait_compat(sem, NULL);
+}
+
+int
+_libc_sem_trywait_compat(sem_t *sem)
+{
+	int val;
+
 	if (sem_check_validity(sem) != 0)
 		return (-1);
 
-	return (ksem_timedwait((*sem)->semid, abs_timeout));
+	if ((*sem)->syssem != 0)
+ 		return ksem_trywait((*sem)->semid);
+
+	while ((val = (*sem)->count) > 0) {
+		if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
+			return (0);
+	}
+	errno = EAGAIN;
+	return (-1);
 }
 
 int
-__sem_post(sem_t *sem)
+_libc_sem_post_compat(sem_t *sem)
 {
 
 	if (sem_check_validity(sem) != 0)
 		return (-1);
 
-	return (ksem_post((*sem)->semid));
+	if ((*sem)->syssem != 0)
+		return ksem_post((*sem)->semid);
+
+	atomic_add_rel_int(&(*sem)->count, 1);
+
+	if ((*sem)->nwaiters)
+		return _umtx_wake(&(*sem)->count);
+	return (0);
 }
 
 int
-__sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
+_libc_sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval)
 {
 	int retval;
 
@@ -351,10 +470,7 @@ __sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
 	if ((*sem)->syssem != 0)
 		retval = ksem_getvalue((*sem)->semid, sval);
 	else {
-		_pthread_mutex_lock(&(*sem)->lock);
 		*sval = (int)(*sem)->count;
-		_pthread_mutex_unlock(&(*sem)->lock);
-
 		retval = 0;
 	}
 	return (retval);
diff --git a/lib/libc/gen/sem_new.c b/lib/libc/gen/sem_new.c
new file mode 100644
index 0000000..dac5381
--- /dev/null
+++ b/lib/libc/gen/sem_new.c
@@ -0,0 +1,470 @@
+/*
+ * Copyright (C) 2010 David Xu <davidxu@freebsd.org>.
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice(s), this list of conditions and the following disclaimer as
+ *    the first lines of this file unmodified other than the possible
+ *    addition of one or more copyright notices.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice(s), this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include "namespace.h"
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <errno.h>
+#include <machine/atomic.h>
+#include <sys/umtx.h>
+#include <limits.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <semaphore.h>
+#include <unistd.h>
+#include "un-namespace.h"
+
+__weak_reference(_libc_sem_close, sem_close);
+__weak_reference(_libc_sem_close, _sem_close);
+__weak_reference(_libc_sem_destroy, sem_destroy);
+__weak_reference(_libc_sem_destroy, _sem_destroy);
+__weak_reference(_libc_sem_getvalue, sem_getvalue);
+__weak_reference(_libc_sem_getvalue, _sem_getvalue);
+__weak_reference(_libc_sem_init, sem_init);
+__weak_reference(_libc_sem_init, _sem_init);
+__weak_reference(_libc_sem_open, sem_open);
+__weak_reference(_libc_sem_open, _sem_open);
+__weak_reference(_libc_sem_post, sem_post);
+__weak_reference(_libc_sem_post, _sem_post);
+__weak_reference(_libc_sem_timedwait, sem_timedwait);
+__weak_reference(_libc_sem_timedwait, _sem_timedwait);
+__weak_reference(_libc_sem_trywait, sem_trywait);
+__weak_reference(_libc_sem_trywait, _sem_trywait);
+__weak_reference(_libc_sem_unlink, sem_unlink);
+__weak_reference(_libc_sem_unlink, _sem_unlink);
+__weak_reference(_libc_sem_wait, sem_wait);
+__weak_reference(_libc_sem_wait, _sem_wait);
+
+#define SEM_PREFIX	"/tmp/SEMD"
+#define SEM_MAGIC	((u_int32_t)0x73656d31)
+
+struct sem_nameinfo {
+	int open_count;
+	char *name;
+	sem_t *sem;
+	LIST_ENTRY(sem_nameinfo) next;
+};
+
+static pthread_once_t once = PTHREAD_ONCE_INIT;
+static pthread_mutex_t sem_llock;
+static LIST_HEAD(,sem_nameinfo) sem_list = LIST_HEAD_INITIALIZER(sem_list);
+
+static void
+sem_prefork()
+{
+	
+	_pthread_mutex_lock(&sem_llock);
+}
+
+static void
+sem_postfork()
+{
+	_pthread_mutex_unlock(&sem_llock);
+}
+
+static void
+sem_child_postfork()
+{
+	_pthread_mutex_unlock(&sem_llock);
+}
+
+static void
+sem_module_init(void)
+{
+	pthread_mutexattr_t ma;
+
+	_pthread_mutexattr_init(&ma);
+	_pthread_mutexattr_settype(&ma,  PTHREAD_MUTEX_RECURSIVE);
+	_pthread_mutex_init(&sem_llock, &ma);
+	_pthread_mutexattr_destroy(&ma);
+	_pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
+}
+
+static inline int
+sem_check_validity(sem_t *sem)
+{
+
+	if (sem->_magic == SEM_MAGIC)
+		return (0);
+	else {
+		errno = EINVAL;
+		return (-1);
+	}
+}
+
+int
+_libc_sem_init(sem_t *sem, int pshared, unsigned int value)
+{
+
+	if (value > SEM_VALUE_MAX) {
+		errno = EINVAL;
+		return (-1);
+	}
+ 
+	bzero(sem, sizeof(sem_t));
+	sem->_magic = SEM_MAGIC;
+	sem->_kern._count = (u_int32_t)value;
+	sem->_kern._has_waiters = 0;
+	sem->_kern._flags = pshared ? USYNC_PROCESS_SHARED : 0;
+	return (0);
+}
+
+sem_t *
+_libc_sem_open(const char *name, int flags, ...)
+{
+	char path[PATH_MAX];
+
+	struct stat sb;
+	va_list ap;
+	struct sem_nameinfo *ni = NULL;
+	sem_t *sem = NULL;
+	int fd = -1, mode, len;
+
+	if (name[0] != '/') {
+		errno = EINVAL;
+		return (NULL);
+	}
+	name++;
+
+	if (flags & ~(O_CREAT|O_EXCL)) {
+		errno = EINVAL;
+		return (NULL);
+	}
+
+	_pthread_once(&once, sem_module_init);
+
+	_pthread_mutex_lock(&sem_llock);
+	LIST_FOREACH(ni, &sem_list, next) {
+		if (strcmp(name, ni->name) == 0) {
+			ni->open_count++;
+			sem = ni->sem;
+			_pthread_mutex_unlock(&sem_llock);
+			return (sem);
+		}
+	}
+
+	if (flags & O_CREAT) {
+		va_start(ap, flags);
+		mode = va_arg(ap, int);
+		va_end(ap);
+	}
+
+	len = sizeof(*ni) + strlen(name) + 1;
+	ni = (struct sem_nameinfo *)malloc(len);
+	if (ni == NULL) {
+		errno = ENOSPC;
+		goto error;
+	}
+
+	ni->name = (char *)(ni+1);
+	strcpy(ni->name, name);
+
+	strcpy(path, SEM_PREFIX);
+	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
+		errno = ENAMETOOLONG;
+		goto error;
+	}
+
+	fd = _open(path, flags|O_RDWR, mode);
+	if (fd == -1)
+		goto error;
+	if (flock(fd, LOCK_EX) == -1)
+		goto error;
+	if (_fstat(fd, &sb)) {
+		flock(fd, LOCK_UN);
+		goto error;
+	}
+	if (sb.st_size < sizeof(sem_t)) {
+		sem_t tmp;
+
+		tmp._magic = SEM_MAGIC;
+		tmp._kern._has_waiters = 0;
+		tmp._kern._count = 0;
+		tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
+		if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp)) {
+			flock(fd, LOCK_UN);
+			goto error;
+		}
+	}
+	flock(fd, LOCK_UN);
+	sem = (sem_t *)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE,
+		MAP_SHARED|MAP_NOSYNC, fd, 0);
+	if (sem == MAP_FAILED) {
+		sem = NULL;
+		if (errno == ENOMEM)
+			errno = ENOSPC;
+		goto error;
+	}
+	if (sem->_magic != SEM_MAGIC) {
+		errno = EINVAL;
+		goto error;
+	}
+	ni->open_count = 1;
+	ni->sem = sem;
+	LIST_INSERT_HEAD(&sem_list, ni, next);
+	_pthread_mutex_unlock(&sem_llock);
+	_close(fd);
+	return (sem);
+
+error:
+	_pthread_mutex_unlock(&sem_llock);
+	if (fd != -1)
+		_close(fd);
+	if (sem != NULL)
+		munmap(sem, sizeof(sem_t));
+	free(ni);
+	return (SEM_FAILED);
+}
+
+int
+_libc_sem_close(sem_t *sem)
+{
+	struct sem_nameinfo *ni;
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	if (!(sem->_kern._flags & SEM_NAMED)) {
+		errno = EINVAL;
+		return (-1);
+	}
+
+	_pthread_mutex_lock(&sem_llock);
+	LIST_FOREACH(ni, &sem_list, next) {
+		if (sem == ni->sem) {
+			if (--ni->open_count > 0) {
+				_pthread_mutex_unlock(&sem_llock);
+				return (0);
+			}
+			else
+				break;
+		}
+	}
+
+	if (ni) {
+		LIST_REMOVE(ni, next);
+		_pthread_mutex_unlock(&sem_llock);
+		munmap(sem, sizeof(*sem));
+		free(ni);
+		return (0);
+	}
+	_pthread_mutex_unlock(&sem_llock);
+	return (-1);
+}
+
+int
+_libc_sem_unlink(const char *name)
+{
+	char path[PATH_MAX];
+
+	if (name[0] != '/') {
+		errno = ENOENT;
+		return -1;
+	}
+	name++;
+
+	strcpy(path, SEM_PREFIX);
+	if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
+		errno = ENAMETOOLONG;
+		return (-1);
+	}
+	return unlink(path);
+}
+
+int
+_libc_sem_destroy(sem_t *sem)
+{
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	if (sem->_kern._flags & SEM_NAMED) {
+		errno = EINVAL;
+		return (-1);
+	}
+	sem->_magic = 0;
+	return (0);
+}
+
+int
+_libc_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
+{
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	*sval = (int)sem->_kern._count;
+	return (0);
+}
+
+static int
+usem_wake(struct _usem *sem)
+{
+	if (!sem->_has_waiters)
+		return (0);
+	return _umtx_op(sem, UMTX_OP_SEM_WAKE, 0, NULL, NULL);
+}
+
+static int
+usem_wait(struct _usem *sem, const struct timespec *timeout)
+{
+	if (timeout && (timeout->tv_sec < 0 || (timeout->tv_sec == 0 &&
+	    timeout->tv_nsec <= 0))) {
+		errno = ETIMEDOUT;
+		return (-1);
+	}
+	return _umtx_op(sem, UMTX_OP_SEM_WAIT, 0, NULL,
+			__DECONST(void*, timeout));
+}
+
+int
+_libc_sem_trywait(sem_t *sem)
+{
+	int val;
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	while ((val = sem->_kern._count) > 0) {
+		if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
+			return (0);
+	}
+	errno = EAGAIN;
+	return (-1);
+}
+
+static void
+sem_cancel_handler(void *arg)
+{
+	sem_t *sem = arg;
+
+	if (sem->_kern._has_waiters && sem->_kern._count)
+		usem_wake(&sem->_kern);
+}
+
+#define TIMESPEC_SUB(dst, src, val)                             \
+        do {                                                    \
+                (dst)->tv_sec = (src)->tv_sec - (val)->tv_sec;  \
+                (dst)->tv_nsec = (src)->tv_nsec - (val)->tv_nsec; \
+                if ((dst)->tv_nsec < 0) {                       \
+                        (dst)->tv_sec--;                        \
+                        (dst)->tv_nsec += 1000000000;           \
+                }                                               \
+        } while (0)
+
+
+static int
+enable_async_cancel(void)
+{
+	int old;
+
+	_pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &old);
+	return (old);
+}
+
+static void
+restore_async_cancel(int val)
+{
+	_pthread_setcanceltype(val, NULL);
+}
+
+int
+_libc_sem_timedwait(sem_t * __restrict sem,
+	const struct timespec * __restrict abstime)
+{
+	struct timespec ts, ts2;
+	int val, retval, saved_cancel;
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	retval = 0;
+	_pthread_testcancel();
+	for (;;) {
+		while ((val = sem->_kern._count) > 0) {
+			if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
+				return (0);
+		}
+
+		if (retval)
+			break;
+
+		/*
+		 * The timeout argument is only supposed to
+		 * be checked if the thread would have blocked.
+		 */
+		if (abstime != NULL) {
+			if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
+				errno = EINVAL;
+				return (-1);
+			}
+			clock_gettime(CLOCK_REALTIME, &ts);
+			TIMESPEC_SUB(&ts2, abstime, &ts);
+		}
+		pthread_cleanup_push(sem_cancel_handler, sem);
+		saved_cancel = enable_async_cancel();
+		retval = usem_wait(&sem->_kern, abstime ? &ts2 : NULL);
+		restore_async_cancel(saved_cancel);
+		pthread_cleanup_pop(0);
+	}
+	return (retval);
+}
+
+int
+_libc_sem_wait(sem_t *sem)
+{
+	return _libc_sem_timedwait(sem, NULL);
+}
+
+/*
+ * POSIX:
+ * The sem_post() interface is reentrant with respect to signals and may be
+ * invoked from a signal-catching function. 
+ * The implementation does not use lock, so it should be safe.
+ */
+int
+_libc_sem_post(sem_t *sem)
+{
+
+	if (sem_check_validity(sem) != 0)
+		return (-1);
+
+	atomic_add_rel_int(&sem->_kern._count, 1);
+	if (sem->_kern._has_waiters)
+		return usem_wake(&sem->_kern);
+	return (0);
+}
diff --git a/lib/libc/include/libc_private.h b/lib/libc/include/libc_private.h
index 052eb13..cb0b407 100644
--- a/lib/libc/include/libc_private.h
+++ b/lib/libc/include/libc_private.h
@@ -127,6 +127,8 @@ typedef enum {
 	PJT_SETSPECIFIC,
 	PJT_SIGMASK,
 	PJT_TESTCANCEL,
+	PJT_CLEANUP_POP_IMP,
+	PJT_CLEANUP_PUSH_IMP,
 	PJT_MAX
 } pjt_index_t;
 
diff --git a/lib/libthr/pthread.map b/lib/libthr/pthread.map
index 62f3ff5..0ade298 100644
--- a/lib/libthr/pthread.map
+++ b/lib/libthr/pthread.map
@@ -145,13 +145,6 @@ FBSD_1.0 {
 	recvfrom;
 	recvmsg;
 	select;
-	sem_destroy;
-	sem_getvalue;
-	sem_init;
-	sem_post;
-	sem_timedwait;
-	sem_trywait;
-	sem_wait;
 	sendmsg;
 	sendto;
 	sigaction;
@@ -348,13 +341,6 @@ FBSDprivate_1.0 {
 	_pthread_timedjoin_np;
 	_pthread_yield;
 	_raise;
-	_sem_destroy;
-	_sem_getvalue;
-	_sem_init;
-	_sem_post;
-	_sem_timedwait;
-	_sem_trywait;
-	_sem_wait;
 	_sigaction;
 	_sigprocmask;
 	_sigsuspend;
@@ -410,4 +396,11 @@ FBSD_1.1 {
 
 FBSD_1.2 {
 	openat;
+	sem_destroy;
+	sem_getvalue;
+	sem_init;
+	sem_post;
+	sem_timedwait;
+	sem_trywait;
+	sem_wait;
 };
diff --git a/lib/libthr/thread/Makefile.inc b/lib/libthr/thread/Makefile.inc
index 4ce90b5..d3de74e 100644
--- a/lib/libthr/thread/Makefile.inc
+++ b/lib/libthr/thread/Makefile.inc
@@ -41,6 +41,7 @@ SRCS+= \
 	thr_rwlockattr.c \
 	thr_self.c \
 	thr_sem.c \
+	thr_sem_new.c \
 	thr_setprio.c \
 	thr_setschedparam.c \
 	thr_sig.c \
diff --git a/lib/libthr/thread/thr_init.c b/lib/libthr/thread/thr_init.c
index f96bba9..1bfdd28 100644
--- a/lib/libthr/thread/thr_init.c
+++ b/lib/libthr/thread/thr_init.c
@@ -246,7 +246,9 @@ static pthread_func_t jmp_table[][2] = {
 	{DUAL_ENTRY(_pthread_setcanceltype)},	/* PJT_SETCANCELTYPE */
 	{DUAL_ENTRY(_pthread_setspecific)},	/* PJT_SETSPECIFIC */
 	{DUAL_ENTRY(_pthread_sigmask)},		/* PJT_SIGMASK */
-	{DUAL_ENTRY(_pthread_testcancel)}	/* PJT_TESTCANCEL */
+	{DUAL_ENTRY(_pthread_testcancel)},	/* PJT_TESTCANCEL */
+	{DUAL_ENTRY(__pthread_cleanup_pop_imp)},/* PJT_CLEANUP_POP_IMP */
+	{DUAL_ENTRY(__pthread_cleanup_push_imp)}/* PJT_CLEANUP_PUSH_IMP */
 };
 
 static int init_once = 0;
diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
index 57be0ae..415c1ec 100644
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -52,6 +52,20 @@
 #include <sys/thr.h>
 #include <pthread.h>
 
+#define	SYM_FB10(sym)			__CONCAT(sym, _fb10)
+#define	SYM_FBP10(sym)			__CONCAT(sym, _fbp10)
+#define	WEAK_REF(sym, alias)		__weak_reference(sym, alias)
+#define	SYM_COMPAT(sym, impl, ver)	__sym_compat(sym, impl, ver)
+#define	SYM_DEFAULT(sym, impl, ver)	__sym_default(sym, impl, ver)
+
+#define	FB10_COMPAT(func, sym)				\
+	WEAK_REF(func, SYM_FB10(sym));			\
+	SYM_COMPAT(sym, SYM_FB10(sym), FBSD_1.0)
+
+#define	FB10_COMPAT_PRIVATE(func, sym)			\
+	WEAK_REF(func, SYM_FBP10(sym));			\
+	SYM_DEFAULT(sym, SYM_FBP10(sym), FBSDprivate_1.0)
+
 #ifndef __hidden
 #define __hidden		__attribute__((visibility("hidden")))
 #endif
@@ -660,6 +674,9 @@ int	_schedparam_to_rtp(int policy, const struct sched_param *param,
 void	_thread_bp_create(void);
 void	_thread_bp_death(void);
 int	_sched_yield(void);
+void	_thr_sem_prefork(void);
+void	_thr_sem_postfork(void);
+void	_thr_sem_child_postfork(void);
 
 void	_pthread_cleanup_push(void (*)(void *), void *);
 void	_pthread_cleanup_pop(int);
diff --git a/lib/libthr/thread/thr_sem.c b/lib/libthr/thread/thr_sem.c
index 0dd5599..f20bde3 100644
--- a/lib/libthr/thread/thr_sem.c
+++ b/lib/libthr/thread/thr_sem.c
@@ -36,7 +36,6 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
-#include <semaphore.h>
 #include <stdlib.h>
 #include <time.h>
 #include <_semaphore.h>
@@ -44,248 +43,73 @@
 
 #include "thr_private.h"
 
-
-__weak_reference(_sem_init, sem_init);
-__weak_reference(_sem_destroy, sem_destroy);
-__weak_reference(_sem_getvalue, sem_getvalue);
-__weak_reference(_sem_trywait, sem_trywait);
-__weak_reference(_sem_wait, sem_wait);
-__weak_reference(_sem_timedwait, sem_timedwait);
-__weak_reference(_sem_post, sem_post);
-
-
-static inline int
-sem_check_validity(sem_t *sem)
-{
-
-	if ((sem != NULL) && ((*sem)->magic == SEM_MAGIC))
-		return (0);
-	else {
-		errno = EINVAL;
-		return (-1);
-	}
-}
-
-static sem_t
-sem_alloc(unsigned int value, semid_t semid, int system_sem)
-{
-	sem_t sem;
-
-	if (value > SEM_VALUE_MAX) {
-		errno = EINVAL;
-		return (NULL);
-	}
-
-	sem = (sem_t)malloc(sizeof(struct sem));
-	if (sem == NULL) {
-		errno = ENOSPC;
-		return (NULL);
-	}
-	bzero(sem, sizeof(*sem));
-	/*
-	 * Fortunatly count and nwaiters are adjacency, so we can
-	 * use umtx_wait to wait on it, umtx_wait needs an address
-	 * can be accessed as a long interger.
-	 */
-	sem->count = (u_int32_t)value;
-	sem->nwaiters = 0;
-	sem->magic = SEM_MAGIC;
-	sem->semid = semid;
-	sem->syssem = system_sem;
-	return (sem);
-}
+FB10_COMPAT(_sem_init_compat, sem_init);
+FB10_COMPAT(_sem_destroy_compat, sem_destroy);
+FB10_COMPAT(_sem_getvalue_compat, sem_getvalue);
+FB10_COMPAT(_sem_trywait_compat, sem_trywait);
+FB10_COMPAT(_sem_wait_compat, sem_wait);
+FB10_COMPAT(_sem_timedwait_compat, sem_timedwait);
+FB10_COMPAT(_sem_post_compat, sem_post);
+
+typedef struct sem *sem_t;
+
+extern int _libc_sem_init_compat(sem_t *sem, int pshared, unsigned int value);
+extern int _libc_sem_destroy_compat(sem_t *sem);
+extern int _libc_sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval);
+extern int _libc_sem_trywait_compat(sem_t *sem);
+extern int _libc_sem_wait_compat(sem_t *sem);
+extern int _libc_sem_timedwait_compat(sem_t * __restrict sem,
+    const struct timespec * __restrict abstime);
+extern int _libc_sem_post_compat(sem_t *sem);
+
+int _sem_init_compat(sem_t *sem, int pshared, unsigned int value);
+int _sem_destroy_compat(sem_t *sem);
+int _sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval);
+int _sem_trywait_compat(sem_t *sem);
+int _sem_wait_compat(sem_t *sem);
+int _sem_timedwait_compat(sem_t * __restrict sem,
+    const struct timespec * __restrict abstime);
+int _sem_post_compat(sem_t *sem);
 
 int
-_sem_init(sem_t *sem, int pshared, unsigned int value)
+_sem_init_compat(sem_t *sem, int pshared, unsigned int value)
 {
-	semid_t semid;
-
-	semid = (semid_t)SEM_USER;
-	if ((pshared != 0) && (ksem_init(&semid, value) != 0))
-		return (-1);
-
-	(*sem) = sem_alloc(value, semid, pshared);
-	if ((*sem) == NULL) {
-		if (pshared != 0)
-			ksem_destroy(semid);
-		return (-1);
-	}
-	return (0);
+	return _libc_sem_init_compat(sem, pshared, value);
 }
 
 int
-_sem_destroy(sem_t *sem)
+_sem_destroy_compat(sem_t *sem)
 {
-	int retval;
-
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	/*
-	 * If this is a system semaphore let the kernel track it otherwise
-	 * make sure there are no waiters.
-	 */
-	if ((*sem)->syssem != 0)
-		retval = ksem_destroy((*sem)->semid);
-	else {
-		retval = 0;
-		(*sem)->magic = 0;
-	}
-	if (retval == 0)
-		free(*sem);
-	return (retval);
+	return _libc_sem_destroy_compat(sem);
 }
 
 int
-_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
+_sem_getvalue_compat(sem_t * __restrict sem, int * __restrict sval)
 {
-	int retval;
-
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	if ((*sem)->syssem != 0)
-		retval = ksem_getvalue((*sem)->semid, sval);
-        else {
-		*sval = (int)(*sem)->count;
-		retval = 0;
-	}
-	return (retval);
+	return _libc_sem_getvalue_compat(sem, sval);
 }
 
 int
-_sem_trywait(sem_t *sem)
-{
-	int val;
-
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	if ((*sem)->syssem != 0)
- 		return (ksem_trywait((*sem)->semid));
-
-	while ((val = (*sem)->count) > 0) {
-		if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
-			return (0);
-	}
-	errno = EAGAIN;
-	return (-1);
-}
-
-static void
-sem_cancel_handler(void *arg)
+_sem_trywait_compat(sem_t *sem)
 {
-	sem_t *sem = arg;
-
-	atomic_add_int(&(*sem)->nwaiters, -1);
-	if ((*sem)->nwaiters && (*sem)->count)
-		_thr_umtx_wake(&(*sem)->count, 1, 0);
+	return _libc_sem_trywait_compat(sem);
 }
 
 int
-_sem_wait(sem_t *sem)
+_sem_wait_compat(sem_t *sem)
 {
-	struct pthread *curthread;
-	int val, retval;
-
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	curthread = _get_curthread();
-	if ((*sem)->syssem != 0) {
-		_thr_cancel_enter(curthread);
-		retval = ksem_wait((*sem)->semid);
-		_thr_cancel_leave(curthread);
-		return (retval);
-	}
-
-	_pthread_testcancel();
-	do {
-		while ((val = (*sem)->count) > 0) {
-			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
-				return (0);
-		}
-		atomic_add_int(&(*sem)->nwaiters, 1);
-		THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
-		_thr_cancel_enter(curthread);
-		retval = _thr_umtx_wait_uint(&(*sem)->count, 0, NULL, 0);
-		_thr_cancel_leave(curthread);
-		THR_CLEANUP_POP(curthread, 0);
-		atomic_add_int(&(*sem)->nwaiters, -1);
-	} while (retval == 0);
-	errno = retval;
-	return (-1);
+	return _libc_sem_wait_compat(sem);
 }
 
 int
-_sem_timedwait(sem_t * __restrict sem,
+_sem_timedwait_compat(sem_t * __restrict sem,
     const struct timespec * __restrict abstime)
 {
-	struct timespec ts, ts2;
-	struct pthread *curthread;
-	int val, retval;
-
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	curthread = _get_curthread();
-	if ((*sem)->syssem != 0) {
-		_thr_cancel_enter(curthread);
-		retval = ksem_timedwait((*sem)->semid, abstime);
-		_thr_cancel_leave(curthread);
-		return (retval);
-	}
-
-	/*
-	 * The timeout argument is only supposed to
-	 * be checked if the thread would have blocked.
-	 */
-	_pthread_testcancel();
-	do {
-		while ((val = (*sem)->count) > 0) {
-			if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
-				return (0);
-		}
-		if (abstime == NULL) {
-			errno = EINVAL;
-			return (-1);
-		}
-		clock_gettime(CLOCK_REALTIME, &ts);
-		TIMESPEC_SUB(&ts2, abstime, &ts);
-		atomic_add_int(&(*sem)->nwaiters, 1);
-		THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
-		_thr_cancel_enter(curthread);
-		retval = _thr_umtx_wait_uint((uint32_t*)&(*sem)->count, 0, &ts2, 0);
-		_thr_cancel_leave(curthread);
-		THR_CLEANUP_POP(curthread, 0);
-		atomic_add_int(&(*sem)->nwaiters, -1);
-	} while (retval == 0);
-	errno = retval;
-	return (-1);
+	return _libc_sem_timedwait_compat(sem, abstime);
 }
 
-/*
- * sem_post() is required to be safe to call from within
- * signal handlers, these code should work as that.
- */
-
 int
-_sem_post(sem_t *sem)
+_sem_post_compat(sem_t *sem)
 {
-	int retval = 0;
-	
-	if (sem_check_validity(sem) != 0)
-		return (-1);
-
-	if ((*sem)->syssem != 0)
-		return (ksem_post((*sem)->semid));
-
-	atomic_add_rel_int(&(*sem)->count, 1);
-
-	if ((*sem)->nwaiters) {
-		retval = _thr_umtx_wake(&(*sem)->count, 1, 0);
-		if (retval != 0)
-			retval = -1;
-	}
-	return (retval);
+	return _libc_sem_post_compat(sem);
 }
diff --git a/lib/libthr/thread/thr_sem_new.c b/lib/libthr/thread/thr_sem_new.c
new file mode 100644
index 0000000..689b252
--- /dev/null
+++ b/lib/libthr/thread/thr_sem_new.c
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2010 David Xu <davidxu@freebsd.org>.
+ * All rights reserved.
+ * 
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice(s), this list of conditions and the following disclaimer as
+ *    the first lines of this file unmodified other than the possible
+ *    addition of one or more copyright notices.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice(s), this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
+ * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
+ * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#include "namespace.h"
+#include <sys/types.h>
+#include <sys/queue.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <pthread.h>
+#include <stdlib.h>
+#include <time.h>
+#include <semaphore.h>
+#include "un-namespace.h"
+
+#include "thr_private.h"
+
+__weak_reference(_sem_init, sem_init);
+__weak_reference(_sem_destroy, sem_destroy);
+__weak_reference(_sem_getvalue, sem_getvalue);
+__weak_reference(_sem_trywait, sem_trywait);
+__weak_reference(_sem_wait, sem_wait);
+__weak_reference(_sem_timedwait, sem_timedwait);
+__weak_reference(_sem_post, sem_post);
+
+extern int _libc_sem_init(sem_t *sem, int pshared, unsigned int value);
+extern int _libc_sem_destroy(sem_t *sem);
+extern int _libc_sem_getvalue(sem_t * __restrict sem, int * __restrict sval);
+extern int _libc_sem_trywait(sem_t *sem);
+extern int _libc_sem_wait(sem_t *sem);
+extern int _libc_sem_timedwait(sem_t * __restrict sem,
+    const struct timespec * __restrict abstime);
+extern int _libc_sem_post(sem_t *sem);
+
+int
+_sem_init(sem_t *sem, int pshared, unsigned int value)
+{
+	return _libc_sem_init(sem, pshared, value);
+}
+
+int
+_sem_destroy(sem_t *sem)
+{
+	return _libc_sem_destroy(sem);
+}
+
+int
+_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
+{
+	return _libc_sem_getvalue(sem, sval);
+}
+
+int
+_sem_trywait(sem_t *sem)
+{
+	return _libc_sem_trywait(sem);
+}
+
+int
+_sem_wait(sem_t *sem)
+{
+	return _libc_sem_wait(sem);
+}
+
+int
+_sem_timedwait(sem_t * __restrict sem,
+    const struct timespec * __restrict abstime)
+{
+	return _libc_sem_timedwait(sem, abstime);
+}
+
+int
+_sem_post(sem_t *sem)
+{
+	return _libc_sem_post(sem);
+}
diff --git a/sys/kern/uipc_sem.c b/sys/kern/uipc_sem.c
index 5ca13f8..f41b49c 100644
--- a/sys/kern/uipc_sem.c
+++ b/sys/kern/uipc_sem.c
@@ -51,7 +51,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/priv.h>
 #include <sys/proc.h>
 #include <sys/posix4.h>
-#include <sys/semaphore.h>
 #include <sys/_semaphore.h>
 #include <sys/stat.h>
 #include <sys/syscall.h>
diff --git a/sys/sys/_semaphore.h b/sys/sys/_semaphore.h
index df3c5da..5266d04 100644
--- a/sys/sys/_semaphore.h
+++ b/sys/sys/_semaphore.h
@@ -31,26 +31,9 @@
 typedef intptr_t semid_t;
 struct timespec;
 
-#ifndef _KERNEL
-
-#include <sys/cdefs.h>
+#define SEM_VALUE_MAX  __INT_MAX
 
-/*
- * Semaphore definitions.
- */
-struct sem {
-#define SEM_MAGIC       ((u_int32_t) 0x09fa4012)
-        u_int32_t       magic;
-        pthread_mutex_t lock;
-        pthread_cond_t  gtzero;
-        u_int32_t       count;
-        u_int32_t       nwaiters;
-#define SEM_USER        (NULL)
-        semid_t         semid;  /* semaphore id if kernel (shared) semaphore */
-        int             syssem; /* 1 if kernel (shared) semaphore */
-        LIST_ENTRY(sem) entry;
-        struct sem      **backpointer;
-};
+#ifndef _KERNEL
 
 __BEGIN_DECLS
 
diff --git a/sys/sys/semaphore.h b/sys/sys/semaphore.h
deleted file mode 100644
index 34ede7b..0000000
--- a/sys/sys/semaphore.h
+++ /dev/null
@@ -1,69 +0,0 @@
-/*-
- * Copyright (c) 1996, 1997
- *	HD Associates, Inc.  All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by HD Associates, Inc
- * 4. Neither the name of the author nor the names of any co-contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY HD ASSOCIATES AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL HD ASSOCIATES OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * $FreeBSD$
- */
-
-/* semaphore.h: POSIX 1003.1b semaphores */
-
-#ifndef _SEMAPHORE_H_
-#define _SEMAPHORE_H_
-
-#include <machine/_limits.h>
-
-/* Opaque type definition. */
-struct sem;
-typedef	struct sem *	sem_t;
-
-#define	SEM_FAILED	((sem_t *)0)
-#define	SEM_VALUE_MAX	__INT_MAX
-
-#ifndef _KERNEL
-#include <sys/cdefs.h>
-
-struct timespec;
-
-__BEGIN_DECLS
-int	 sem_close(sem_t *);
-int	 sem_destroy(sem_t *);
-int	 sem_getvalue(sem_t * __restrict, int * __restrict);
-int	 sem_init(sem_t *, int, unsigned int);
-sem_t	*sem_open(const char *, int, ...);
-int	 sem_post(sem_t *);
-int	 sem_timedwait(sem_t * __restrict, const struct timespec * __restrict);
-int	 sem_trywait(sem_t *);
-int	 sem_unlink(const char *);
-int	 sem_wait(sem_t *);
-__END_DECLS
-
-#endif
-
-#endif /* !_SEMAPHORE_H_ */